Friday, May 31, 1805. We proceeded in two periogues, leaving the canoes to bring on the meat of two buffaloes killed last evening. Soon after we set off it began to rain, and though it ceased at noon, the weather continued cloudy during the rest of the day. The obstructions of yesterday still remain and fatque the men excessively; The banks are so slippery in some places and the mud so adhesive that they are unable to wear their moccasins; one forth of the time they are obliged to be up to their armpits in the cold water, and sometimes walk for several yards over the sharp fragments of rocks which have fallen from the hills; all this added to the burden of dragging the heavy canoes is very painful, yet the men bear it with great patience and good humour. Once the rope of one of the perigues, the only one we had made of hemp, broke short, and the periogue swung and just touched a point of rock which almost overset her. At nine miles we came to a high wall of black rock rising from the water's edge on the south, above the cliffs of the river; this continued about a quarter of a mile, and was succeeded by a high open plain, thill three miles further a second wall two hundred feet high rose on the same side. Three miles further a wall of the same kind about two hundred feet high and twelve in thickness, appeared to the north; these hills and river cliffs exibit a most extrodinary and romantic appearance; they rise in most places nearly perpendicular from the water, to the height of between two and three hundred feet, and are formed of very white sandstone, so soft as to yeild readily to the impression of the water, in the upper part of which lie imbedded two or three thin horizontal stratas of white freestone insensible to the rain, and on the top is a dark rich loam, which forms a gradually ascending plain, from a mile to a mile and a half in extent, when the hills again rise abruptly to the hieght of about three hundred feet more. In trickling down the cliffs, the water has worn the soft sandstone into a thousand grotesque figures, among with which a little fancy may be discerned elegant ranges of freestone buildings, with columns variously sculptured, and supporting long and elegant galleries, while the parapets are adorned with statuary; on a nearer approach they represent every form of elegant ruins; columns, some with pedestals and capitals entire, others mutilated and prostrate, and some rising pyramidally over each other till they terminate in a sharp point. These are varied by niches, alcoves, and the customary appearances of desolated mafnificence; the allusion is increased by the of martins, who have built their globular nests in the niches and hover over these columns; as in our country they are accustomed to frequent large stone structures. As we advance ther seems no end to the visionary enchantment which surrounds us. In the midst of this fantastic scenery are vast ranges of walls, which seem the productions of art, so regular is the workmanship; they rise perpendicularly from the river, sometimes to the height of one hundred feet, varing in thickness from one to twelve feet, being equally broad at the top as below. The stones of which they are formed are black, thick, and durable, and composed of a large portion of earth, intermixed and cemented with a small quantity of sand, and a considerable proportion of talk or quartz. These stones are almost invariably regular parallelipeds of unequal sizes in the wall, but equally deep, and laid regularly in ranges over each other like bricks, each breaking and covering the interstice of the two on which it rests; but though the perpendicular interstice be destroyed, the horizontal one extends entirely through the whole work; the stones too are proportioned to the thickness of the wall in which they are employed, being largest in the thickest walls. The thinner walls are composed of a single depth of the paralleliped, while the thicker ones consist of two or more depths; these walls pass the river at several places, rising from the water's edge much above the sandstone bluffs which they seem to penetrate; thence they cross in a straight line on either side fo the river, the plains over which they tower to the height of from ten to seventy feet, until they lose themselves in the second range of hills; sometimes they run parallel in several ranges near to each other, sometimes intersect each other at right angles, and have the appearance of walls of ancient houses or gardens.

Monday, May 20th, 1805 - As usual we set out early, and the banks being convenient for that purpose, we used the towline; the river is narrow and crooked, the water rapid, and the country much like that of yeaterday; at the distance of two and quater miles we passed a large creek with but little water, to which we gave the name of Blowingfly creek, from the quantity of those insects found in its neighbourhood, They are extremely troublsome, infesting our meat whilst cooking and at our meals. After making seven miles we reached by eleven o'clock the mouth of a large river on the south, and encamped for the day at the upper point of its junction with the Missouri. This stream which we suppose to be that called by the Minnetarees the Mussleshell River, empties into the Missouri two thousand two hundred and seventy miles above the mouth of the latter river. It is 110 yards wide, and contains more water than streams of that size usually do in this country; its current is by no means rapid, and there is every appearence of its being susceptible of navigation by canoes for a considerable distance; its bed is chiefly formed of coarse sand and gravel, with an occasional mixture of black mud; the banks abrupt and nearly twelve feet high, so that they are secure from being overflowed; the water is of a greenish yellow cast and much more transparent than that of the Missouri, which itself, though clearer than below, still retains its whitish hue and a portion of its sediment. Opposite to the point of junction the current of the Missouri is gentle, and 220 yards in width, the bed pricipally of mud and still to deep to use the setting-pole. If this be, as we suppose, the Musselshell, our Indian information is, that it rises in the first chain of the Rocky Mountains not far from the sources of the Yellowstone, whence in its course to this place it waters a high broken country, well timbered particularly on its borders, and interspersed with handsome fertile plains and meadows. We have reason, however, to believe, from them giving a similar account of the timber where we are now, that the timber of which they speak is similer to that which we have seen for a few days past, which consists of nothing more than a few straggling small pine and dwarf ceder, on the summits of the hills. The also reported that the country is broken and irregular like that near our camp; that about five miles up a handsome river about fifty yards wide, which we named after Chaboneau's wife, Sahcajahweah, or Birdwomen's river, discharges itself into the Musselshell on the north or upper side. Another party found at the foot of the southern hills, about four miles from the Missouri, a fine bold spring, which in this country is so rare that since we left the Mandans we have found one of a similar kind, and that was under the bluffs on the south side of the Missouri, at some distance from it, and about five miles below the Yellowstone; with this exception all the small fountains of which we have met a number are impregnated with the salts which are so abundant here, and with which the Missouri is itself most probably tainted, though to us who have been so mush accustomed to it, the taste is not perceptible. Among the game today we observed two large owls, with remarkably long feathers resembling ears on the sides of the head, which we presume are the hooting owls, though they are larger and their colors are brighter than those common in the United States.